1. Field of the Invention
The present invention relates to structures for storing communications cables, and particularly to apparatus for storing slack fiber optic cabling.
2. Discussion of the Known Art
Fiber optic switching centers typically house a number of pieces of switching and routing equipment in rooms where floor space is at a premium. While exact locations for each piece of equipment may be planned prior to installation, the installers often do not situate the equipment precisely at those locations for various reasons. Also, fiber optic cables that are routed to the equipment are costly since they must be supplied with factory installed connectors to accommodate as many as, e.g., 72 fibers in each cable. If only one fiber in a cable is found to have an unacceptable high insertion loss, then a new cable with pre-installed connectors must be substituted since the old cable cannot be repaired in the field.
Therefore, to ensure that cables in a switching center are able to reach the equipment to which they are routed and a worst-case scenario of a “short” cable does not occur, the cables are made longer than would be needed if each piece of equipment was installed exactly where planned. The excess cable length is referred to as “slack”, and cables that connect to the equipment will have a certain amount of slack that must be taken up and properly stowed near the associated equipment to avoid cable damage. For example, in a modern switching center, as much as 60 feet of slack may exist for each of a number of fiber optic cables associated with a single router.
So-called cable troughs in the form of open rectangular channels may be used to store cable slack. See, for example, U.S. Pats. No. 6,318,680 (Nov. 20, 2001), No. 6,470,129 (Oct. 22, 2002), and No. 7,034,227 (Apr. 25, 2006). With respect to fiber optic cables, however, care must be taken to lay the cable in the trough so that no part of the cable is urged toward a position where it will assume less than a certain minimum bend radius. Otherwise, one or more fibers in the cable may break or become irreparably damaged. This constraint may be difficult to realize if a slack portion of the cable must be layered by folding on itself in order to contain all the slack inside the trough.
U.S. Pat. No. 6,487,356 (Nov. 26, 2002) discloses apparatus that provides storage for fiber optic cable slack, and for segregation of cables at the front and the back sides of a line bay chassis. Slack spool assemblies are fixed at either side of the chassis to provide for storage of fiber optic cables routed toward the top and at the bottom of the chassis. Slack storage trays and holders constructed to limit the bend of optical fibers are also known. See, e.g., U.S. Pats. No. 6,580,866 (Jun. 17, 2003), No. 7,295,747 (Nov. 13, 2007), and No. 7,346,253 (Mar. 18, 2008).
A need remains, however, for apparatus than can store long lengths of slack presented by many fiber optic cables routed to various pieces of equipment at a switching center or elsewhere, within a relatively small volume and without damaging the cable fibers.